Electrical resistivity and 57Fe Mössbauer spectra of Fe-bearing calcic amphiboles

Electrical resistivity and ⁵⁷Fe Mössbauer spectra are reported for three calcic amphiboles with different Fe concentrations. AC measurements (20?Hz–1?MHz) were performed, applying impedance spectroscopy between 100 and 785?°C in an N₂ gas atmosphere. It was found that up to three semiconducting charge transport processes can be distinguished, which in part changed slightly when several runs were carried out to higher temperatures. The extrapolated DC resistivity is much smaller for an amphibole with high Fe content than for the two with lower Fe concentrations. The derived activation energies are between ～0.48 and ～1.06?eV. For temperatures ≤600?°C the results are compatible with a charge transport mechanism due to electron hopping between Fe²⁺ and Fe³⁺. Above 600?°C, dehydrogenation and/or beginning amphibole decomposition obviously alter the conduction mechanism. From Mössbauer spectra it was established that in all amphibole samples Fe²⁺ and Fe³⁺ are simultaneously present. Mössbauer parameters were derived by fitting the observed spectra to models taking the occupation of various M sites into account.     

A highstand oolitic sequence and associated facies from a Late Triassic lake basin, south-west England

High energy, lake‐shoreline carbonate sequences are rarely documented in the geological record. However, one example occurs in the Upper Triassic Mercia Mudstone Group (MMG) of southern Britain. The MMG is one of a number of thick, non‐fossiliferous mudstone deposits associated with North Atlantic Mesozoic rift basins. The origin of the MMG mudstones is the subject of current debate, with marine, playa‐lacustrine and alluvial–aeolian models having been proposed. Shoreline features have been documented from the northern margin of the basin, but the rarity of such features elsewhere in the MMG has led many workers to doubt a lacustrine origin for the mudstones. Wave‐dominated, lake‐shoreline deposits have been recognized in several sections from the southern basin margin in the Clevedon area of the Bristol Channel in south‐west England. These deposits provide evidence for the development of a sizeable perennial to semi‐perennial hypersaline lake in which the MMG mudstones accumulated. Shoreline sediments overlie alluvial stream and sheet‐flood deposits, and pass from transgressive gravel–conglomerate beach units with bioclasts, influenced by shore‐normal waves (deposited under semi‐humid conditions), to lower gradient, highstand oolitic sands affected by more varied wave approach (deposited under progressively more arid conditions), which culminated in lowstand, oolitic strand‐plain deposits overlain by a playa‐mudflat unit. Shoreline deposits record a simple shallowing‐upward transgressive–highstand–lowstand sequence. However, a change from a reflective (transgressive) to dissipative (highstand) shoreline is believed to represent a climatically induced change in prevailing wind direction. Shoreline features recognized in the MMG are similar to those of recent playa‐lacustrine basins of the western United States. Ooids display a variety of size, fracture and dissolution features in addition to beachrock fabrics, suggesting that they were originally composed of radial aragonite, similar to modern ooids from the Great Salt Lake, Utah.     

塔里木盆地三叠系烃源岩有机岩石学特征与生烃评价

应用现代有机岩石学方法，配合有机地球化学方法，通过对塔里木盆地三叠系烃源岩的研究，认识了一种较特殊的烃源岩类型，其生烃母质以菌解无定形体为主，不仅其实测镜质组反射率Ｒ°具有明显抑制作用，而且其生烃早，“液态窗”范围介于镜质组Ｒ°为０．４０％－０．９５％之间。这类烃源岩生烃潜力较强（相当于ⅡＢ型干酪根），实际上已进入成熟－成烃峰期阶段，并广泛分布于塔北轮南及其以南地区，预测展布面积达１．０－１．５万     

内蒙古西拉木伦断裂带韧性变形特征

西拉木伦断裂带在早二叠世末发生了韧性右行走滑,形成了包括韧性右行走滑带、韧性压扁带及弱韧性变形带在内的韧性变形带。据动力和运动分析,表明该韧性变形带为一普通剪切带,其中韧性右行走滑带在平面上以简单剪切为主,韧性压扁带在平面上以纯剪切为主。     

古鄱阳湖盆地东北缘白晋纪地层的新材料—兼论陆相地层清理后的问题讨论

古鄱阳湖盆地东北缘白垩系的田坂群历来趋向“二分”，但从对剖在再观察入手，认为田坂群纵向上经历了粗→细→粗的巨旋回，这种巨旋回与盆地演化规律，发展阶段相一致，因而“三分”显著，该剖面地学，9沉积学的一些新发现，不仅便于地层划分与对比，而且对盆内层序地层，岩相分析，构造演化阶段研究都具重要意义。     

东昆仑祁漫塔格地区乌兰乌珠尔早古生代花岗岩锆石U-Pb年代学、地球化学及其地质意义

为确定东昆仑祁漫塔格乌兰乌珠尔地区片麻状黑云母花岗岩和二长花岗岩的形成时代、岩石成因、源区性质和构造背景,对该岩石样品进行了锆石U-Pb年代学、地球化学和锆石Hf同位素研究.结果显示:片麻状黑云母花岗岩加权平均年龄为457.5±2.3 Ma,铝饱和指数A/CNK介于0.98～1.02,属准铝质岩石,Na2O/K2O比值...     

广元上寺剖面下三叠统飞仙关组风暴岩:巨型季风体制下的极端气候事件?

早三叠世扬子地台位于特提斯东北缘,研究者根据大量地质证据和模拟实验证实该时期巨型季风强度最大,且控制了整个泛大陆和周边海域的气候循环.笔者于川西北广元上寺剖面下三叠统中发现一套保存完好的风暴岩,其发育于飞仙关组下部,风暴沉积特征明显,风暴侵蚀构造、风暴撕裂构造和层理构造发育;根据沉积构造、岩石性质等识别了Sa-Sb-S...     

New Study of Anshunsaurus huangnihensis Cheng, 2007 (Reptilia: Thalattosauria): Revealing its Transitional Position in Askeptosauridae

The skull of Anshunsaurus huangnihensis Cheng, 2007, especially the skull roof, is described in detail in this paper. Compared to other genera and species of Askeptosauroidea, Anshunsaurus huangnihensis has some important transitional characters from Askeptosaurus italicus to Anshunsaurus huangguoshuensis: the rostral length related to the skull length between Askeptosaurus italicus and Anshunsaurus huangguoshuensis; the postfrontal existing but distinctly reduced; the posterolateral process relatedly short and overlapping the parietal. The phylogenetic analysis weakly supports the evolutional progress from Anshunsaurus huangnihensis to Anshunsaurus huangguoshuensis. The skeletal ratios indicated that the node among the Askeptosauridae ingroup. The evolutional direction of Askeptosauridae should be from Askeptosaurus italicus to Anshunsaurus huangguoshuensis. The skeletal ratios indicated that the evolutional progress is Askeptosaurus italicus – Anshunsaurus huangnihensis – Anshunsaurus huangguoshuensis. In biogeography provinces, the Askeptosauroidea taxa from south China have a close relationship with those from western Tethys; however, Xinpusaurus from the Late Triassic is more related to those from the eastern Pacific.     

新疆觉罗塔格小热泉子组火山岩的时代探讨

新疆东天山觉罗塔格地区广泛分布着石炭系-二叠系火山岩-沉积岩地层,小热泉子组是其中的一套以火山岩为主的地层.前人依据与之接触的底坎尔组中的中石炭世化石,将小热泉子组划为早石炭世.对觉罗塔格南部的小热泉子铜矿的研究,不同学者得出了差别较大的同位素年龄,而北部的小热泉子组目前还没有同位素年龄报道.我们对北部的底坎尔和干沟两地的小热泉子组火山岩进行了锆石SHRIMP测年,得到了271～275 Ma的年龄.这些测年数据与近几年其他学者的数据一致,表明早二叠世的岩浆活动比原来认为的更广,小热泉子组的时代应该属于早二叠世,其他地层单元的时代及其先后关系也需要重新认识.     

和田地区二叠—下三叠统层序地层特征与沉积体系

据陆相层序地层学原理及野外露头层序地层学方法,对新疆和田地区桑株、杜瓦、皮牙曼、阿其克等剖面的二叠—下三叠统进行层序界面识别,建立了和田地区层序地层格架.研究表明,该区二叠—下三叠统共划分为5个Ⅲ级层序及12个体系域.研究区在不同时期共发育5种沉积体系类型,包括冲积扇体系、河流沉积体系、湖泊沉积体系、三角洲体系及扇三角洲体系,指出该区层序演化中有利的烃源层、储集层和盖层及组合.